Full vacuum heat insulation box body and method for producing and disassembling the same

ABSTRACT

A heat insulation box body includes inner and outer boxes forming a shell of the heat insulation box body and triangular structural materials inserted in the shell held by close-contact by means of a vacuum. Further, at the time of disassembling the heat insulation box body after scrapping, a shell surface is cut and air is introduced into the inside of the shell to return the state of the shell to an atmospheric pressure state and then respective members are separated from each other.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to heat insulation walls requiringheat insulation in a heat insulation box body such as a refrigerator, orthe like, in which wall surfaces are formed of thin metal plates, resinmoldings, or the like. More particularly, the present invention relatesto a full vacuum heat insulation box body in which porous structuralmaterials are disposed in a shell constituting heat insulation walls forthe purpose of preventing deformation so that a vacuum is kept, arefrigerator using such a full vacuum heat insulation box body, a methodfor producing such a full vacuum heat insulation box body, and a methodfor disassembling such a full vacuum heat insulation box body.

[0003] 2. Description of the Related Art

[0004] Conventionally, a shell of a refrigerator, or the like, is soconstituted that an outer box is formed of a thin metal plate such as aniron plate, an inner box is formed of a resin molding, and closed-cellfoaming urethane used for forming a structural material, is injectedinto a gap between the inner and outer boxes and foamed so that the gapis filled with the structural material.

[0005]FIG. 16 is a flow chart illustrating a process of producing aconventional refrigerator using closed-cell foaming urethane as a heatinsulating material in walls, and FIG. 17 illustrates a foaming urethaneinjection step in the process.

[0006] That is, in a conventional refrigerator, or the like, an innerbox 2 obtained by attaching necessary members, such as an anchor forfixing interior parts, piping for supplying a refrigerant, etc., to avacuum molding of an ABS resin sheet, is inserted in an outer box 1 of aformed product obtained by bending a steel plate to thereby form ashell. Injection portions 4 are provided in the outer box 1 (step 1) toinject a mixture solution 3 of foaming urethane.

[0007] After sheet metal worked parts are attached to the back andbottom portions which are residual opening portions, a slight gap ineach engaging portion is sealed with a hot melt adhesive agent, or thelike, and further interior parts are partially assembled (step 2).

[0008] The thus obtained box body is laid down as shown in FIG. 17, andfixed in a foaming jig heated to an arbitrary temperature. After amixing head 5 is successively inserted into and fixed to injection holesof the injection portions 4 provided in the outer box 1, a mixturesolution 3 of foaming urethane is discharged and injected. Then,injection portions 4 are sealed with plugs. Because the foaming urethanemixture solution 3, at the time of injection, is a liquid having anexpansion ratio in a range from several times to tens of times, themixture solution 3 flows in a flange portion corresponding to theopening portions of the box body through the injection portion 4 so asto disperse. Further, after some seconds, a foaming agent is vaporizedby reaction heat of raw materials and thereby the foam is caused to fillthe residual gap between the inner box 2 and the outer box 1 withurethane foam. A heat insulation box body thus formed can be taken outfrom the foaming jig after some minutes, generally about 5 minutes fromthe injection (step 3).

[0009] Residual parts, for example, electric parts such as a fan motorand a light and interior parts such as shelves and various kinds ofcasings are put in the thus obtained heat insulation box body. Afterrefrigerant circuit securing parts for securing a refrigerant circuitare attached to the heat insulation box body, the refrigerant circuit ischarged with a refrigerant. Thus, assembling of the product is completed(step 4).

[0010] Inspection of various kinds of functions of the completed productis carried out through an actual operation so as to confirm that theproduct is not defective (step 5).

[0011] When a package and documents pertinent to the obtained productare prepared and added, the production is completed (step 6).

[0012] It has been found that the chlorine containing1,1-dichloro-1-fluoroethane (HFC141b), which is one ofhydrochlorofluorocarbons that has been used as a foaming agent forforming urethane foam used as a heat insulating material herein, is acause of ozone layer destruction. Accordingly, use of hydrofluorocarbonsor hydrocarbons which do not contain chlorine in their molecules, hasbeen proposed in recent years.

[0013] For example, a method for producing urethane foam by use ofhydrofluorocarbons such as 1,1,1,3,3-pentafluoropropane (HFC245fa) and1,1,1,4,4,4-hexafluorobutane (HFC356mffm) as a foaming agent isdisclosed in JP-A-2-235982, and a method for producing urethane foam byuse of hydrocarbon such as cyclopentane, or the like, as a foaming agentis disclosed in JP-A-3-152160.

[0014] However, the heat insulating property of such urethane foam is ina range from 19 to 20 mw/MK and clearly inferior to the heat insulatingproperty of 16 mw/MK of chlorofluorocarbons used before issue ofregulations on use of ozone layer destruction substances.

[0015] Since the improvement of the heat insulating property of urethanefoam has reached a limit, a technique of applying a vacuum heatinsulation panel which has more than twice as higher heat insulatingproperty as the urethane foam as shown in the comparison view of FIG. 18has been proposed for a refrigerator, or the like, allowing a reductionof electric power consumption without use of any substance which causesozone layer destruction.

[0016] For example, JP-A-60-243471 discloses a heat insulation box bodyin which a member obtained by putting pulverized PUF in a syntheticresin bag and vacuum-packing the pulverized PUF in the form of a boardis disposed inside walls, and JP-A-60-60483 proposes a refrigerator inwhich a vacuum heat insulation panel having a gap which is provided inthe flange side of a side plate to allow PUF to flow in the gap isdisposed in a side wall of the refrigerator.

[0017] The vacuum heat insulation panel such as those proposed above,has a structure shown in FIG. 19. A method for producing the vacuum heatinsulation panel will be described below. First, a core material 11having a porous structure such as an aggregate of fibers or particles, afoam having open cells, or the like, is inserted into a bag-like packingmaterial 12. Then, in order to generate a high quality heat insulatingproperty, its inside is deaerated by using a vacuum panel making machine15 comprising fusion-bonding devices 17 each having a heater 17 a,sealing pressure devices 18, and a vacuum control valve 16 as shown inFIG. 20. While a vacuum state is maintained, end edge portions 12 a ofthe packing material 12 containing the core material 11 are heat-sealedto prevent external air from entering inside. Thus, a vacuum heatinsulation panel 13 shown in FIG. 19 is obtained. Preferably, the insideof the vacuum panel making machine 15 is kept to 10⁻² torr when the endedge portions 12 a are subjected to fusion bonding. Therefore,adjustment of the degree of vacuum is performed by use of the vacuumcontrol valve 16 connected to an evacuator not shown.

[0018] Accordingly, in the packing material 12, a thin metal film layeris used as its intermediate layer for blocking or suppressing entranceof gas from the outside into the vacuum heat insulation panel to therebykeep a heat insulating property. A material having excellent weldingproperty is used as its inner layer so that insertion openings can besealed perfectly, and a material for stably securing adhesion tourethane foam is used as its surface layer so that generation ofscratches is suppressed and bending strength of walls in a box body suchas a refrigerator, or the like, can be secured. Because the packingmaterial 12 is required to have various characteristics as describedabove, a multilayer sheet in which different materials are laminated tosatisfy the required characteristics is used.

[0019] Further, the core material 11 must have a strength higher thanatmospheric pressure to satisfy a function of holding the panel shape ina vacuum state and the quantities of conducted heat (heat conduction)and penetrated heat (heat radiation) through a substance constitutingthe core material itself must be suppressed to thereby contribute toimprovement of heat insulating property. Accordingly, a porous plateformed of a substance with small heat transfer rate is used as the corematerial 11.

[0020] That is, in order to improve the heat insulating property of thevacuum heat insulating panel 13, it is important to use a substance thatis a good insulator for the core material 11 among constituentmaterials, reduces the heat-conduction area of the material to suppressthe heat conduction through the substance, and reduces the gap tosuppress heat radiation. As a substance satisfying the aforementionedconditions, a porous material of resin, glass, or the like, ispreferably used. In particular, a mat of glass fiber, a board of a resinfoam having open cells, or a molding of resin or inorganic fineparticles is used preferably.

[0021] For example, JP-A-60-71881 has proposed a material obtained byputting pearlite powder in a synthetic resin bag and vacuum-packing itinto the form of a board. Similarly, JP-A-60-243471 has proposed amaterial obtained by putting pulverized PUF in a synthetic resin bag andvacuum-packing it into the form of a board. As other proposals,JP-A-60-205164 has proposed hard polyurethane foam having open cells,JP-A-4-218540 has proposed a plate-like molding which is formed fromthermoplastic urethane resin powder firmly bonded and, JP-A-7-96580 hasproposed a board which comprises long glass fiber, fibrillated resinfiber and inorganic fine powder, each of which is applied as a corematerial of the vacuum heat insulation panel.

[0022] Each of the vacuum heat insulation panels, such as those proposedabove, is generally shaped as a board or a substrate having a thicknessin a range from 10 to 20 mm and is typically incorporated into the wallof the refrigerator. That is, after the inner box is inserted into theouter box equipped with the vacuum heat insulation panels stuck thereonso that the inner box is united with the outer box, a raw materialmixture solution of foaming urethane is injected thereto, foamed andmolded to thereby form a heat insulation wall.

[0023] Accordingly, in the case of a refrigerator, the vacuum heatinsulation panel is usually not stuck on the inner box having an unevensurface for shelf rests, or the like, but fixed to the outer box surfaceby use of an adhesive agent, or the like, so that foaming urethane tofill the gap in the shell containing the vacuum heat insulation panelsdisposed therein is fully packed without any remaining gap to therebyprevent spoilage of design characteristic such as deformation, or thelike.

[0024] However, in the cases that the packing material has some finedefect which is larger than expected, a part of the packing material isdestroyed by an external factor or a large amount of volatile substanceremains in or sticks to the core material, thereby creating a number ofpossibilities that a desired heat insulating property cannot beprovided.

[0025] As described above, in the heat insulation wall structure of theconventional heat insulation box body, the vacuum heat insulation panelis disposed in the shell and the residual space is filled with urethanefoam having closed cells. Therefore, if the aforementioned failureoccurs in the vacuum heat insulation panel, it is not only verydifficult to repair the vacuum heat insulation panel but also impossibleto replace the vacuum heat insulation panel with a new one. That is, theheat insulation wall is conventionally formed on the assumption that thewhole of a system such as a heat insulation box body, a refrigerator, orthe like, must be scrapped when the aforementioned failure occurs.

[0026] As a method to enable lowering of the degree of vacuum caused bythe aforementioned possibilities to be repaired, there has been proposeda heat insulation box body having heat insulation walls in which all theinside of the shell of the heat insulation box body is set in a vacuumstate. For example, JP-A-57-52783 has proposed to insert anair-permeable bag containing a powder substance into the gap between theinner and outer boxes, JP-A-3-140782 has proposed to put particles ofpearlite, or the like, into the hollow resin shell, and JP-A-2-192580and JP-A-7-148752 have proposed to inject foaming heat insulatingmaterial such as foaming urethane with open cells into the shell. Eachof the shells is evacuated with a vacuum pump, or the like, through agas exhaust hole provided in a part of the shell to secure the vacuumstate inside the shell of the heat insulation box body.

[0027] In the conventional heat insulation box body configured so thatall the heat insulation wall is kept in a vacuum state as describedabove, it has been found that it is very difficult to fill the inside ofthe shell with a powder or granular substance uniformly and densely whenthe powder or granular substance is put in the shell. Accordingly, ifthe inside of the shell is kept in a vacuum state, the shell is pressedby atmospheric pressure so as to be partly or wholly contracted, so thatdeterioration of design characteristic may be caused or in some cases,deterioration of heat insulating property caused by reduction of thewall thickness may be triggered.

[0028] Further, in filling a heat insulation box body having inferiorfilling property such as a large-size refrigerator, or the like, alarger amount of filling is required than the amount of fillingcorresponding to the density for obtaining a strength required toprevent deformation caused by the atmospheric pressure.

[0029] Accordingly, there arise disadvantages such as economical loss,increase of weight, lowering of heat insulating property, etc.

[0030] Further, in filling the heat insulation box body with open-cellfoaming urethane, communication of bubbles cannot be sufficientlyachieved so that closed cells remain, if bubbles in a foamed state flowover a short distance from the start point of foaming, bubbles flow in astate of stable shape after completion of bubble growth, and so on.

[0031] Further, because foaming gas remaining in bubbles remains incells or is adsorbed into a resin constituting cells even in a portionin which communication of cells is achieved, foaming gas remains.Accordingly, if this is used as it is, for a structural material, therearises a disadvantage that not only a long time is required forevacuation particularly of a large-size full vacuum heat insulation boxbody but also a degree of vacuum changes is lost over the passage oftime.

[0032] That is, in accordance with the aforementioned proposals, it isindispensable to perform troublesome evacuation substantiallyperiodically by use of a vacuum pump, or the like, or to incorporate asuction system for the purpose of preventing a drop in the degree ofvacuum due to generation of gas in the shell. Furthermore, in a statewhere the inside of the shell is filled with no gap, a long evacuationtime is required because this structure brings a great disadvantage forsucking remaining gas in an opposite portion inside the shell to thegas-exhaust hole up to all open cells through a long distance along opencells by use of a vacuum pump from a gas-exhaust hole provided in an endportion of the heat insulation box body such as a refrigerator, or thelike, to thereby perform evacuation to secure a sufficient vacuum state.Further, during the period when the degree of vacuum drops with thepassage of time, a cooling operation is carried out frequently, so thatelectric power is additionally consumed and the temperature of theinside of the refrigerator becomes unstable to cause a problem in thatthe freshness of foods is affected.

[0033] Further, when the full vacuum heat insulation box body obtainedby the conventional production method is to be disassembled afterscrapping so as to recycle parts or members, some measures are requiredto prevent scattering of the filling materials at the time ofdisassembling or collecting in the former case of filling powder orgranular materials, and it is also difficult to handle the materialswithout damage even in the case of employing a method in which thefilling materials are disposed in a form protected by bags, or the like.

[0034] On the other hand, in the latter case of the full vacuum heatinsulation box body in which a raw-material mixture solution of foamingurethane is injected into the shell and foamed to thereby form heatinsulation walls, the filled urethane foam firmly self-adheres to theinner and outer boxes constituting the shell so as to be nearlyinseparable therefrom when the box body is to be disassembled afterscrapping to recycle the members. In the conventional method therefore,the shell is not separated into constituent members but the inner andouter boxes and the filled urethane foam self-adhering thereto arecollectively subjected to a crusher so as to be broken up, and then, thecrushed parts are separated into respective members by use of aseparation method using weight or magnetic characteristic arranged for asubsequent step to the crusher, so that the outer box is magneticallyattached, the inner box is made to fall down by itself by weight and theurethane foam is flown off, for example, laterally by use of wind, orthe like. It is however impossible to perfectly separate the urethanefoam self-adhering to the inner and outer boxes from adhering surfaces.Accordingly, used members cannot be reused and therefore, recycling ofthe members is difficult using the conventional methods.

SUMMARY OF THE INVENTION

[0035] A technical object of the present invention is to entirely holdthe inside of heat insulation walls in a vacuum state as well as toprovide easy evacuation, light-weight and uniform strength, reduction ofremaining gas and prevention of entrance of gas from the outside, andalso to facilitate disassembling after scrapping of the heat insulationwalls so as to simplify recycling of respective members.

[0036] In order to achieve the above object, according to one aspect ofthe present invention, a full vacuum heat insulation box body in whichthe inside of its heat insulation walls is filled with structuralmaterials having continuous pores and kept in a vacuum state, isconstructed such that inner and outer boxes constituting a shell of theheat insulation box body and the structural material put between theinner and outer boxes are held only by close-contact caused by means ofa vacuum. With this configuration, the constituent materials of the boxbody can be separated and collected easily when disassembling the boxbody after scrapping, without leaving material on the abutting parts.

[0037] Preferably, the shell of the heat insulation box body has anuneven surface, and the structural materials abutting on the unevensurface of the shell include moldings formed of a pulverized resin foam.With this configuration, a non-filling portion is not produced betweenthe uneven surface of, for example, the inner box and the abuttingsurface of the structural materials, so that flaws in designcharacteristic such as surface deformation can be prevented even in thecase where the inside of the shell is kept in a vacuum.

[0038] Preferably, the structural materials contain parts comprisinggrooves or holes for exhausting air and continuous pores. With thisconfiguration, gas such as air remaining in the shell can be exhaustedeasily, resulting in a short time required for evacuation and a highdegree of vacuum secured to improve heat insulating property.

[0039] Preferably, the structural materials are constituted by a resinfoam having open cells. With this configuration, heat insulation wallswith small heat conduction can be formed, so that the quantity ofleaking heat can be suppressed and heat insulating properties can beimproved.

[0040] Preferably, the structural materials have parts each having atriangular section, each of the triangular-section parts being disposedin a middle layer in the direction of wall thickness, or in a layerabutting an even surface of the shell. With this configuration, a wedgeeffect is obtained so that the walls are never slackened or deformed,and an inferior design characteristic such as deformation can beprevented.

[0041] Preferably, the parts having a triangular section are formed ofpolystyrene foam having open cells. With this configuration, dust, orthe like, is never produced even if surfaces of the parts are rubbed inhandling, moderate flexibility necessary for handling is provided toimprove working efficiency, and a strength tolerant to the atmosphericpressure and a fine cell shape are provided to provide both excellentexternal appearance and heat insulating property.

[0042] Preferably, the polystyrene foam having open cells has flattenedcells which are spread in a direction perpendicular to the direction ofwall thickness. With this configuration, the effect of blockingradiation heat in a heat-insulating direction are improved.

[0043] Preferably, a joint portion between the inner and outer boxes isconstituted by a groove of a predetermined depth formed by bending oneof the boxes and is filled with a liquid substance having an adhesivesealing function and an end side portion formed in the other box so asto be able to be inserted into a deep portion of the groove. Joining andsealing of the joint portion are performed by the liquid substance byutilizing mutual attraction force produced at the time of evacuation ofthe shell. With this configuration, the inner and outer boxes canoperate as a piston. Structural materials can be pressed from theoutside by the inner and outer boxes, so that the degree ofclose-contact between the structural materials can be enhanced on thebasis of a vacuum.

[0044] Preferably, an opening portion, which is later closed with aplate member, for inserting the structural materials is provided in theouter box, a joint portion between the outer box and the plate member isconstituted by a groove of a predetermined depth formed by bending oneof the outer box and the plate member and filled with a liquid substancehaving an adhesive sealing function and an end side portion formed inthe other of them so as to be able to be inserted into a deep portion ofthe groove. Joining and sealing of the joint portion are performed bythe liquid substance by utilizing mutual attraction force produced atthe time of evacuation of the shell. With this configuration, the platemember can operate as a piston. Structural materials disposed in theopening portion can be pressed from the back side by the plate member,so that the degree of close-contact between the structural materials canbe enhanced on the basis of a vacuum.

[0045] Preferably, the groove is formed by bending an end edge portioninward in a zigzag arrangement. With this configuration, a gapcontinuous along the whole circumference of the joint portion can beformed between a base end piece of the zigzag bent portion and the outercircumferential surface of the outer box and the distance from the outerbox to the structural materials can be made longer. Accordingly, at thetime of disassembling after scrapping an opposite portion of the outercircumferential surface of the outer box to the base end piece of thezigzag bent portion can be cut easily without keeping cutting depthaccurate. Accordingly, air can be introduced inside and the shell can beopened easily, so that respective structural materials can be taken outwithout damage and collected.

[0046] Preferably, the groove has a wide reservoir portion at its upperportion for reserving a liquid substance to prevent it from overflowingfrom the groove. With this configuration, the shell can be filled withan amount of adhesive agent sufficient to seal and the adhesive agentcan be also prevented from overflowing to the outside, so as to improveworkability and prevent both staining of a core material with theadhesive agent and adhesion of structural materials to the shell by theadhesive agent.

[0047] Preferably, the liquid substance is constituted by an adhesiveagent containing particles or powder of a metal oxide or a metal nitrideWith this configuration, permeation of various kinds of gasses, watervapors, etc. can be suppressed, so that degradation of heat insulatingproperty caused by vacuum loss over time can be prevented.

[0048] Preferably, a mark or indicia is provided in the outercircumferential surface of the zigzag bent portion. With thisconfiguration, a portion to be cut without damage of structuralmaterials to be collected can be easily found at the time ofdisassembly.

[0049] According to another aspect of the present invention, a methodfor producing a full vacuum heat insulation box body includesintegrating an inner box and an outer box onto a first shell which isopened in an open bottom surface of the outer box, inserting a firststructural material having continuous pores and a triangular sectioninto the inside of a space formed between the inner and outer boxesconstituting the first shell through the opening of the first shell, byinserting a bottom side portion of the first structural material ahead,inserting a second structural material having continuous pores and atriangular section into the space through the opening of the first shellby inserting a vertex portion of the second structural material ahead tothereby fill the inside of the room of the first shell, blocking theopening of the first shell with a third structural material havingcontinuous pores and a shape like a flat plate, enclosing the thirdstructural material with a plate member from the outside to seal thejoint portion between the plate member and the first shell to therebyform a second shell which is fully closed, and evacuating the secondshell. With this method, a heat insulation box body, in which the insideof the shell is kept in a vacuum and its external appearance is neverdeformed, can be obtained easily.

[0050] Preferably, a structural material to be brought into contact withan uneven surface of the shell is first inserted and a triangularsectional structural material having no uneven surface is finallyinserted with a vertex portion thereof inserted ahead, so that the roomof the first shell is filled with the structural materials. With thisconfiguration, structural materials abut on the shell without any gap,so that tight wall surfaces can be obtained easily.

[0051] Preferably, evacuation of the second shell is performed under thecondition that the inner and outer boxes and the structural materialsput between the inner and outer boxes are not fixed by an adhesiveagent, or the like. With this configuration, structural materials can bedisposed of easily, so that working efficiency is improved and theadhesive agent which is a cause of lowering of the degree of vacuum inthe shell can be eliminated to suppress loss of vacuum.

[0052] Preferably, at least one member of the first shell and the platemember for covering the opening of the first shell is bent at the jointportion to form a groove of a predetermined depth, the groove is filledwith a liquid substance formed of an adhesive agent containing particlesor powder of a metal oxide or a metal nitride, and after the othermember is inserted into the groove filled with the liquid substance, theliquid substance is solidified while evacuating the fully closed secondshell to thereby perform both joining and sealing at the joint portion.With this configuration, positioning can be made easily and the jointportion can be sealed securely.

[0053] According to a further aspect of the present invention, a methodfor disassembling a full vacuum heat insulation box body having a shellconstituted by inner and outer boxes, and structural materials disposedin the shell, the inner and outer boxes and the structural materialsbeing merely fixed by close-contact caused by means of a vacuum includescutting a surface of the shell to thereby introduce air into the insideof the shell so as to allow the inside state of the shell to return toan atmospheric pressure state, then separating the materials of theshell and the structural materials from each other. With this method,the inner and outer boxes and structural materials can be separated fromeach other by a simple operation of destroying the vacuum state.Accordingly, respective members can be collected and recycled easily.

[0054] Preferably, a joint portion between the inner and outer boxes isconstituted by a groove formed by bending an end edge portion of onemember of the boxes inward in a zigzag and filled with a liquidsubstance, and an end side portion formed in the other member of theboxes so as to be able to be inserted into a deep portion of the groove.Also, preferably, cutting of the shell surface is performed by providinga notch in an outer surface of the one member having the zigzag bentportion along a position corresponding to the zigzag bent portion, andthe inner and outer boxes are then separated from each other and thematerials of the shell and the structural materials are recovered. Withthis configuration, as the cut portion of the shell is apart from astructural material is so as to have a gap between them, this portioncan be cut easily without keeping cutting depth of the notch accurateand the shell can be opened. Accordingly, respective structuralmaterials in the inside of the shell can be taken out, collected andrecycled without damage.

[0055] Preferably, the outer box has an opening portion used forinsertion of structural materials which is closed with a plate member,and a joint portion between the outer box and the plate memberconstituted by a groove formed by bending an end edge portion of onemember of the outer box and the plate member inward in a zigzag andfilled with a liquid substance, and an end side portion formed in theother member of them so as to be able to be inserted into a deep portionof the groove. Cutting of the shell surface is performed by providing anotch in an outer circumferential surface of the member having thezigzag bent portion along a position corresponding to the zigzag bentportion, and the outer box and the plate member are then separated fromeach other and the materials of the shell and the structural materialsare recovered. With this configuration, since the cut portion of theshell is separate from a structural material so as to have a gap betweenthem, this portion can be cut easily without keeping cutting depth ofthe notch accurate, and the shell can be opened. Accordingly, respectivestructural materials in the inside of the shell can be taken out,collected and recycled easily without damage.

BRIEF DESCRIPTION OF THE DRAWINGS

[0056]FIG. 1 is a sectional view showing a full vacuum heat insulationbox body according to a first embodiment of the present invention in thestate where the full vacuum heat insulation box body is laid on itsside;

[0057]FIG. 2 is an enlarged sectional view showing a shell constituentmember joint portion which is a main part of the full vacuum heatinsulation box body according to the first embodiment;

[0058]FIG. 3 is a sectional view taken along the line A-A in FIG. 1;

[0059]FIG. 4 is a flow chart showing a method for producing the fullvacuum heat insulation box body according to the first embodiment;

[0060]FIG. 5 is a perspective view showing a refrigerator using the fullvacuum heat insulation box body according to the first embodiment in thestate where a door portion is removed;

[0061]FIG. 6 is a sectional view showing a full vacuum heat insulationbox body according to a second embodiment of the present invention inthe state where the full vacuum heat insulation box body is laid on itsside;

[0062]FIG. 7 is an enlarged sectional view showing the portion B in FIG.6 before joining;

[0063]FIG. 8 is a perspective view showing the whole of a groovedstructural material in the full vacuum heat insulation box bodyaccording to the second embodiment:

[0064]FIG. 9 is a perspective view showing a refrigerator using the fullvacuum heat insulation box body according to a fourth embodiment of thepresent invention in the state where a door portion is removed;

[0065]FIG. 10 is an explanatory view showing a section taken along theline C-C in FIG. 9;

[0066]FIG. 11 is an explanatory view showing a section taken along theline D-D in FIG. 9;

[0067]FIG. 12 is a flow chart showing a method for producing the fullvacuum heat insulation box body according to the fourth embodiment;

[0068]FIG. 13 is an explanatory view showing a method for disassemblinga full vacuum heat insulation box body according to a fifth embodimentof the present invention;

[0069]FIG. 14 is a perspective view showing the full vacuum heatinsulation box body according to the fifth embodiment;

[0070]FIG. 15 is an enlarged sectional view showing a shell constituentmember joint portion which is a main part of the full vacuum heatinsulation box body according to the fifth embodiment;

[0071]FIG. 16 is a flow chart showing steps for producing a conventionalrefrigerator.

[0072]FIG. 17 is an explanatory view showing a foaming urethaneinjection step in the conventional refrigerator producing process;

[0073]FIG. 18 is an explanatory view showing heat insulating property invarious kinds of heat insulating materials;

[0074]FIG. 19 is a sectional view showing the structure of a vacuum heatinsulation panel; and

[0075]FIG. 20 is a sectional view showing the configuration of a vacuumpanel making machine.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0076] Embodiment 1

[0077] The present invention will be described below on the basis of anembodiment as shown in the drawings.

[0078] As shown in FIG. 1, the full vacuum heat insulation box body inthis embodiment is applied to a chest freezer and so designed that innerand outer boxes 22 and 23 which constitute a shell 21 of the heatinsulation box body and structural materials with continuous pores 24,25, 26 and 35 which are interposed between the inner and outer boxes 22and 23 and are preserved only by close contact based on a vacuum.

[0079] In more detail, a box-like member formed by stainless steel thinplates welded or jointed with bond is used herein as the inner box 22constituting an interior surface of the shell 21. The material of thismember is selected taking such conditions into consideration assuppression of lowering of heat insulating property caused bypropagation of heat from the outer box 23 constituting an exteriorsurface of the shell 21, a gas barrier property for suppressinginfiltration of external gas through inner box surfaces, and toleranceto shock caused by falling of various kinds of frozen and preservedfood.

[0080] Further, a four-side bent member formed of a colored steel platecapable of bending is used herein as an outer box 23 constituting theexterior surface of the shell 21, preferably as a box-shaped member inwhich side wall surfaces are integrated. Incidentally, one ofcircumferential side surfaces (four surfaces) of each of the inner andouter boxes 22 and 23 is not shown in Figures for the sake ofconvenience in explanation.

[0081] Among the structural materials 24,25, 26 and 35, structuralmaterials 24, 25 and 35 inserted inside the respective side walls of theshell 21 are composed of parts 24 a and 24 b, 25 a and 25 b, and 35 aand 35 b, respectively, each of which exhibits a triangular sectionalstructure to produce a wedge effect. Among the parts 24 a, 24 b, 25 a,25 b, 35 a and 35 b, the parts 24 a, 25 a and 35 a disposed on the outersides in the inside of the side walls are set to be longer than parts 24b, 25 b and 35 b disposed on the inner sides as shown in FIG. 1 so thatthe vertex ends of the outer parts 24 a, 25 a and 35 a are protrudedfrom the base ends of the inner parts 24 b, 25 b and 35 b to the shellbottom surface side when the parts are assembled.

[0082] Further, a thickness of a rectangular flat plate-like structuralmaterial 26 finally inserted in the bottom wall portion of the shell 21is so set that the structural material 26 is slightly protruded outwardfrom the opening surface of the bottom wall. Furthermore, inclinedsurfaces 26 a corresponding to the inclinations of the outer parts 24 a,25 a and 35 a of the side wall structural materials are formed in thecircumferential surfaces of the structural material 26 so that theinclined surfaces 26 a abut on the inner surfaces of the protrudedportions of the outer parts 24 a, 25 a and 35 a respectively. Inaddition, outer circumferential portions 26 b of the inner surface ofthe structural material 26 are designed to abut on the base end surfacesof the inner parts 24 b, 25 b and 35 b, respectively, of the side wallstructural materials.

[0083] Each of these structural materials 24, 25, 26 and 35 is producedby cutting a large slab formed of a resin foam, such as urethane foam,or the like, having open cells. This is because, since the chest freezeris designed without an uneven portion in the surfaces of the inner andouter boxes 22 and 23, and the structural materials can abut on theinner and outer boxes 22 and 23 having simple shapes formed from planes,insertion of structural materials obtained by cutting a large slabformed of a resin foam, such as urethane foam, or the like, having opencells is inexpensive and materials having various adaptive properties,such as resistance against fragility enough to prevent generation ofdust or the like in the case of rubbing of surfaces at the time ofhandling, strength enough to endure atmospheric pressure, moderateflexibility necessary for handling, excellent heat insulating propertycreated on the basis of the shape of a fine cell effective for radiationheat insulation, the low density needed to suppress heat conduction insolid matters, etc. are secured easily.

[0084] Incidentally, the bottom surface portion of the shell 21constituting a surface opposite to the opening portion of the chestfreezer is opened initially so that the respective structural materials24, 25, 26 and 35 can be inserted. After the respective structuralmaterials 24, 25, 26 and 35 are inserted, the opening of the bottomsurface is closed with a plate member 27 from the outside and the jointportion of the plate member 27 is sealed to thereby form a fully closedbox body. Further, evacuation is performed through a vacuum valve 28fitted to the plate member 27 by welding. As a result, the shell 21constituted by the inner and outer boxes 22 and 23 and the plate member27 comes into contact with the respective structural materials 24, 25,26 and 35 interposed between the constituent members and the contactstate is thus kept. In this occasion, a joint portion 29 between theouter box 23 and the plate member 27 is constituted by a groove 32 of apredetermined depth which is formed by bending an end edge portion ofthe outer box 23 inward in zigzag, as shown in FIG. 2, so that it isfilled with a liquid adhesive agent 31 having a sealing function, and anend side portion 33 so formed in the plate member 27 that it can beinserted deeply into the groove 32. The outer box 23 and the platemember 27 are joined to each other at the joint portion 29 by use ofmutual attraction force caused by negative pressure produced at the timeof evacuation of the inside of the shell and this state is kept untilthe adhesive agent 31 in the groove 32 is hardened, so that the outerbox 23 and the plate member 27 are joined and sealed. In this manner,the plate member 27 is made to operate as a piston by use of thenegative pressure caused by the evacuation at the time of jointing, sothat the structural material 26 disposed in the opening of the bottomsurface can be pressed by the plate member 27 from the back surfaceside. Further, the inner parts 24 b, 25 b and 35 b of the structuralmaterials 24, 25 and 35 inserted in the side wall portion of the shell21 are pressed by the pressed structural material 26, so that the wedgeeffect can be brought.

[0085] Incidentally, an adhesive agent comprising a mixture of a liquidresin such as an epoxy resin and ceramics containing metal oxide ormetal nitride particles or powder is used as the adhesive agent 31. Bythis, contraction accompanying the effect of the resin constituting theadhesive agent 31 is suppressed to thereby prevent occurrence of defectsof passing through the adhesive portion and prevent transmission ofvarious kinds of gases.

[0086] A wide reservoir portion 34 for reserving the adhesive agent 31is provided in the upper portion of the groove 32 by sheet bending asshown in FIG. 2, so that the adhesive agent 31 charged in the groove 32is prevented from overflowing and leaking when the end side portion 33of the plate member 27 is inserted. By this configuration, the end sideportion 33 of the plate member 27 can be received in the groove 32easily, so that the plate member 27 can be fixed to a fixed position ofthe outer box 23. Accordingly, the adhesive agent 31, which may beexcessive but is never insufficient in quantity, can be charged, so thatthe sealing function for blocking entrance of the outside air isenhanced. That is, by immersing the joint portion between the outer box23 and the plate member 27 in the resin charged in the groove 32, afully sealed shell structure is obtained, so that defects such asincomplete joining and communicating portions, etc. can be eliminated.Incidentally, this joint structure is employed not only in the jointportion between the outer box 23 and the plate member 27 but also in ajoint portion (not shown) between the inner and outer boxes 22 and 23.By this configuration, efficiency in joining work and the degree ofsealing of the heat insulation box body as a whole can be enhanced, sothat high reliability is obtained.

[0087] In this manner, the end edge portion of the outer box 23 is bentinward in a zigzag configuration to thereby form the groove 32, and anextreme end side piece 23 a of the zigzag bent portion is bent so as toform the wide reservoir portion 34 for receiving the adhesive agent 31.Accordingly, as shown in FIG. 2, a gap G, which is continuous on thewhole circumference of the joint portion 29, is formed between a baseend side piece 23 b of the zigzag bent portion and a portion 23 c in theouter circumferential surface of the outer box 23 located opposite tothe base end side piece 23 b of the zigzag bent portion. This gap G isnever fixed because the gap G is disposed outside the groove 32 andinside the shell 21 so that it is not filled with the adhesive agent 31.Accordingly, by cutting the zigzag bent portion on the outercircumferential surface of the outer box 23, that is, by cutting theportion 23 c opposite to the base end side piece 23 b at the time ofdisassembling, the air is introduced into the shell 21 so that theinside of the shell 21 can be returned to an atmospheric pressure state.The shell 21 can be thereby opened easily to take out the structuralmaterials 24, 25, 26 and 35.

[0088] Further, as shown in FIG. 3, in each of the corner portions ofthe side walls, the cut shapes of the end edges of the structuralmaterials including the taper of an adjacent triangular structuralmaterial are secured to make close contact to each other, and the endedges of the structural materials are combined in tiers and alabyrinthine form. In each of the corner portions of the side walls,adjacent structural materials can be thereby made to contact closely toeach other, so that the quantity of leaking heat can be greatly reducedeven on condition that of the same gap size is formed in butting.

[0089] A method for producing a full vacuum heat insulation box bodyconfigured as described above will be described below on the basis ofthe flow chart of FIG. 4 with reference to FIGS. 1 through 3. First,stainless steel thin plates are joined by means of welding or adhesivebonding so as to be shaped like a box to thereby obtain an inner box 22constituting an interior surface of a shell of the heat insulation boxbody (step 111).

[0090] Then, a colored steel plate is bent to form a 4-side pipe-likebent member to thereby obtain an outer box 23 constituting an exteriorsurface of the shell of the heat insulation box body. After the innerbox 22 is inserted in the outer box 23, the inner and outer boxes 22 and23 are joined to each other in the joint portions to thereby form afirst shell in which the bottom surface of the outer box is opened (step112). With respect to the work of joining the outer and inner boxes 23and 22, the mode of the joint portions is the same as in the jointportion between the outer box 23 and the plate member 27 explained inFIG. 2. A groove provided in one of the outer and inner boxes 23 and 22is filled with an adhesive agent composed as described above. After anend side portion provided in the other box is inserted in the groovefilled with the adhesive agent, this state is kept until the adhesiveagent in the groove is hardened. Thus, both joining and sealing betweenthe outer and inner boxes 23 and 22 are performed. In this occasion, thegroove can be entirely filled with the adhesive agent if a larger amountof the adhesive agent is provided near the center of each groove so thatthe adhesive agent is made to flow by inserting the end side portion ofthe other box. This is preferable from the point of view of obtaininguniform and faultless sealing. As described above, into the resin in thegroove formed in one of the outer and inner boxes 23 and 22 at the jointportion therebetween, the end side portion provided in the other box isimmersed to thereby make it possible to eliminate defects such asincomplete joined portions and communicating portions, etc. Thus, ashell structure in which the joint portion is fully sealed is obtained.As a result, the defect portion such as a hole passing through theshell, etc. is reduced to secure a sealing structure having an excellentreliability in blocking gas such as air, water vapor, etc. entering theheat insulation box body from the outside.

[0091] Then, a structural material for making the shell endureatmospheric pressure so as not to be deformed at the time of evacuationin the posterior stage, is prepared and inserted in the first shell(step 113). The preparation of the structural material is as follows.First, a foaming resin such as foaming urethane, or the like, havingopen cells is foamed to thereby prepare a large slab-like foamedarticle. The foamed article is cut to obtain first, second and thirdstructural materials, that is, parts 24 a, 25 a and 35 a which are firststructural materials each exhibiting a triangular sectional structure,parts 24 b, 25 b and 35 b which are second structural materials eachexhibiting a triangular sectional structure, and a structural material26 which is a third structural material shaped like a flat plateinserted in the bottom wall portion. The structural materials thusobtained are inserted in gaps between the outer and inner boxes 23 and22 through the opening of the first shell.

[0092] Insertion of the structural materials into the first shell iscarried out as follows. First, the first structural materials eachhaving a triangular section, that is, parts 24 a, 25 a and 35 a areinserted in the inside of respective side walls (4 sides) through theopening of the first shell so as to be preceded by end sides which arerespective base portions of the triangles. Then, the second structuralmaterials each having a triangular section, that is, parts 24 b, 25 band 35 b are inserted in the side walls (4 sides) through the opening ofthe first shell so as to be preceded by vertex portions of thetriangles. By this configuration, the inside of the circumferential sidewalls of the first shell is filled. Then, the opening of the first shellis blocked by the third structural material 26 shaped like a flat plate.

[0093] When insertion of all the structural materials into the firstshell is completed, the third structural material 26 is enclosed by theplate member 27 from the outside to seal the joint portion between theplate member 27 and the first shell with the adhesive agent 31 tothereby form a fully closed second shell (step 114). The second shell isevacuated through the vacuum valve 28 attached to the plate member 27(step 115).

[0094] The evacuation is started under the condition that the structuralmaterials 24, 25, 26 and 35 put between the inner and outer boxes 22 and23 are not fixed by means of an adhesive agent, or the like, and beforethe adhesive agent 31 in the groove 32 in the joint portion 29 betweenthe outer box 23 and the plate member 27 is hardened. The evacuation iscontinued until the adhesive agent 31 is hardened. Accordingly, when theevacuation is started, the plate member 27 is pulled toward the insideof the second shell on the basis of the pressure difference between theair pressure of the inside of the second shell and the air pressure ofthe outside thereof As a result, the plate member 27 functions as apiston for pressing the third structural material 26 from the bottomsurface side. The structural materials 24, 25 and 35 inserted in thecircumferential side wall portions of the shell 21, especially parts 24b, 25 b and 35 b as the second structural materials are pressed by thethird structural material 26 pressed by the plate member 27, so that thewedge effect acts. As a result, there is no slack in the direction ofthe thickness of each wall. so that the shell can be substantiallyentirely filled without any gap. Accordingly, even in the case where theinside of the shell reaches a vacuum state. the shell is never deformed,i.e., cavitated, by the atmospheric pressure. Thus, an excellentexternal appearance state can be kept. After the adhesive agent 31 ishardened, the inner and outer boxes 22 and 23 and the respectivestructural materials 24, 25, 26 and 35 are kept only by close contactbased on a vacuum to thereby obtain a full vacuum heat insulation boxbody which is light in weight and has a uniform strength characteristic(step 116). Although the degree of vacuum in the shell varies inaccordance with the kinds of the structural materials used, sufficientheat insulating property can be provided by keeping the degree of vacuumhigher than 10° torr, preferably higher than 10° torr.

[0095] In this manner, the inner and outer boxes 22 and 23 and therespective structural materials 24, 25, 26 and 35 are brought into closecontact with one another by use of the negative pressure based on avacuum without use of any adhesive agent. Accordingly, the problem ofvaporization, scattering, etc. of water and low-molecular substancescontained in the adhesive agent material, into the shell under a vacuumstate brought about by use of some adhesive agent is eliminated, so thatdegradation of heat insulating property is prevented. Further, althoughthe respective structural materials 24, 25, 26 and 35 are not stuck tothe shell, they fill gaps in the shell. Accordingly, their recomotion,or the like, is not caused by vibration in handling in production anduse and these arises no problem that the external appearance is spoiled.

[0096] Furthermore, recovery at the time of recycling is simplified.That is, in the case of a conventional heat insulation box body such asa refrigerator, or the like, closed-cell urethane foam as a structuralmaterial is firmly stuck to an ABS resin vacuum-molding and a bentarticle of a coated steel plate which are shell materials. Accordingly,in the conventional case, a great deal of labor is required forseparating these materials from each other and the urethane foam cannotbe entirely removed even if these materials are separated. In the fullvacuum heat insulation box body according to the present invention,however, the shell and the structural materials are fixed to one anotherin a state where they are merely pressed by the atmospheric pressure soas to be in close-contact with each other. Accordingly, if the vacuumstate is broken, the inner and outer boxes 22 and 23 and the respectivestructural materials 24, 25, 26 and 35 can be peeled off and separatedeasily.

[0097]FIG. 5 shows a refrigerator produced by the same method as usedfor producing the aforementioned chest freezer. In the case of the chestfreezer, an opening for insertion of the respective structural materialsis provided in the bottom surface, whereas in the case of thisrefrigerator, an opening initially formed for insertion of thestructural materials in the inside of the opposite side walls, aceiling, a floor and a middle wall of the refrigerator is set on theback surface. According to this structure, structural material parts ofa triangular sectional structure inserted in the upper, lower, left,right and middle walls are pressed at the time of evacuation by arectangular flat plate-like structural material finally inserted in theback surface portion and a plate member for enclosing the rectangularflat plate-like structural material, so that the wedge effect can bebrought about. As a result, no slack or cavitation is caused in thedirection of the thickness of each wall, so that the shell can besubstantially entirely filled without any gap. Accordingly, the shell isnever deformed even if the inside of the shell reaches a vacuum state.Thus, a refrigerator having its external appearance kept excellent isobtained. Incidentally, it is a matter of course that the evacuation isperformed at the time of jointing the joint portion between the outerbox 23 and a back plate member (not shown) in a state where therefrigerator is laid on its side, and that the evacuation is startedbefore hardening of the adhesive agent in the groove in the jointportion and continued until the adhesive agent is hardened.

[0098] When the present invention is applied to a large-scale fullvacuum heat insulation box body such as a refrigerator, or the like, asdescribed above, the inner and outer boxes 22 and 23 and the respectivestructural materials can be peeled and separated from one another easilyso that efficiency in recovery at the time of scrapping can be enhancedgreatly. That is, in the conventional heat insulation box body such as arefrigerator, or the like, closed-cell urethane foam as a structuralmaterial is firmly stuck to an ABS resin vacuum-molding and a bentarticle of a coated steel plate as shell materials Accordingly, in theconventional case, a great deal of labor is required for separatingthese materials from each other and urethane foam cannot be entirelyremoved even if these materials are separated. In the full vacuum heatinsulation box body according to the present embodiment, however, theshell and the structural materials are fixed to one another in a statewhere they are merely pressed by the atmospheric pressure so as to be inclose-contact with each other. Accordingly, when the vacuum state isbroken, they can be peeled off and separated easily.

[0099] Embodiment 2

[0100] Referring now to FIG. 6 through FIG. 8, with respect to theinside of the circumferential side walls, only left and right walls areshown and explained.

[0101] In this embodiment, the full vacuum heat insulation box body isapplied to a chest freezer. Parts of structural materials 24 and 25inserted in side walls of a shell 21 constituted by outer and innerboxes 23 and 22 and a plate member 27, that is, parts 24 a, 24 b, 25 aand 25 b each produced by cutting a large slab-like foamed articleformed from a foaming resin such as foaming urethane, or the like,having open cells and exhibiting a triangular sectional structure are sodesigned that a plurality of grooves 41 extending in the lengthwisedirection as shown in FIG. 8 are provided in parallel on an inclinedsurfaces of either one of the inner part 24 a and the outer part 24 b,or 25 a and 25 b. The grooves are herein provided on the inclinedsurfaces of the inner parts 24 b and 25 b disposed on the inner box 22side in this embodiment. The inner parts 24 b and 25 b are combined withthe outer parts 24 a and 25 a disposed on the outer box 23 side so thatthe surfaces of the inner parts 24 b and 25 b having the grooves 41formed thereon come face to face with the surfaces of the outer parts 24a and 25 a. Although the labyrinthine structure of the side edgeportions of the structural materials 24 and 25 is not shown, it is amatter of course that adjacent structural materials are combined witheach other in tiers at each of the corner portions of the side walls.

[0102] In more detail, because wide grooves 41 in the parts 24 b and 25b are easily deformed by atmospheric pressure, it is preferable toprovide a large number of grooves each of which is rather narrow anddeep to an extent not to constitute an obstacle in handling. Here isshown the case where grooves each having a width of 3 mm and a depth of5 mm are provided at intervals of a pitch of 50 mm. The other conditionssuch as the configuration of the joint portion between the outer andinner boxes 23 and 22 and the procedure of assembling the respectivemembers are the same as in the first embodiment described previously.

[0103] Also in this embodiment, by performing evacuation through avacuum valve 28 attached to the plate member 27 by means of welding 42,the wedge effect of the parts 24 b and 25 b each having a triangularsection is brought so that the shell 21 constituted by the inner andouter boxes 22 and 23 and the plate member 27 is brought into closecontact with the structural materials 24, 25 and 26 put therebetween andthat the close contact state is kept. In this occasion, it is necessarythat the gasses in a portion located farthest from the vacuum valve 28(gasses adsorbed on the surface of the shell or remaining in pores ofthe structural materials) are also sucked and exhausted through thevacuum valve 28. In this embodiment, as the grooves 41 serving as gasexhaust passages are present on the mating surface between thetriangular sectional parts of the structural materials 24 and 25inserted in the inside of the respective side walls, gasses, or thelike, in pores of the respective structural materials are exhaustedthrough the grooves 41 after moved into the grooves 41. Accordingly,efficiency evacuation is enhanced so that a sufficient vacuum state canbe secured up to the inside of continuous pores of the structuralmaterials located opposite to the vacuum valve 28.

[0104] For example, in the case of the heat insulation box body of arefrigerator having an internal volume of 400 L, a distance not smallerthan 1 m is required as the distance from a position of evacuation tothe farthest end of the structural materials even if evacuation isperformed from any position. Accordingly, a long time is required toexhaust gasses such as air, etc. remaining in pores of the structuralmaterials located at far ends, only through the pores of the structuralmaterials. According to this embodiment with gas-exhaust grooves 41 onthe contrary, gasses can be exhausted to the outside of the shell easilyafter they are moved into the gas-exhaust grooves 41 so that the timerequired for exhausting gasses is shortened greatly.

[0105] Embodiment 3

[0106] In the full vacuum heat insulation box body according to thisembodiment, the present invention is applied to the same chest freezeras in the first embodiment. Among the structural materials 24, 25, 26and 35 inserted in the inside of the shell 21 constituted by the outerand inner boxes 23 and 22 and the plate member 27 in FIG. 1, at leastparts 24 a, 24 b, 25 a, 25 b, 35 a and 35 b exhibiting a triangularsectional structure are formed of polystyrene foam having open cells.Incidentally, FIGS. 1, 2, 3 and 7 explained previously are referred toin the following description.

[0107] In this embodiment, a resin foam having open cells is used as amaterial for the structural materials 24, 25, 26 and 35. As a material,polystyrene foam having small cell size are used as well as urethanefoam. With respect to a method for producing polystyrene foam havingopen cells, as described in WO96/07942 (JP-A-8-503720, Japanese PatentApplication No. Hei-6-509062) and WO96/16876 (JP-A-8-505895, JapanesePatent Application No. Hei-6-517001), first, polystyrene having a meanmolecular weight of 2×10⁵ is subjected to extrusion mixing, foaming andquenching by suitable use of carbon dioxide gas which is a main foamingagent, and an auxiliary foaming agent such as HFC-134a(1,1,1,2-tetrafluoroethane), HFC-152a (1,1-difluoroethane), etc., sothat polystyrene foam having the open cell content near to 100% and asmall cell size.

[0108] In this occasion, the cells can be flattened easily by additionof compression stress so as to be spread in a direction perpendicular tothe direction of thickness because the temperature of the inside of theobtained extrusion molding having the open cells is kept sufficiently ina value lower than the melting point and higher than the heatdeformation point. In order to remove the stress produced in the resinwhich is involved in flattening of the cells, the temperature is kept inthe compressed state to perform annealing and then the molding is cooledto a temperature lower than the heat deformation point, preferably lowerthan the glass transition point. Among the structural materials 24, 25,26 and 35, structural materials 24, 25 and 35 inserted in the inside ofthe respective side walls of the shell 21 are cut out from the thusobtained molding block into a triangular sectional structure whichbrings about the wedge effect. Further, in the structural materials 24,25 and 35, parts 24 a, 25 a and 35 a disposed on the outer side insidethe side walls are so cut out as to be longer than inner parts 24 b, 25b and 35 b as shown in FIG. 1 so that the vertex side ends of the parts24 a, 25 a and 35 a are protruded toward the bottom surface side of theshell from the base sides of the inner parts 24 b, 25 b and 35 brespectively at the time of assembling. Thus, processed parts eachhaving a desired size and a desired shape are obtained.

[0109] Incidentally, the process of flattening cells may be performedafter the parts 24 a, 24 b, 25 a, 25 b, 35 a and 35 b each exhibiting atriangular sectional structure are cut out from the extrusion moldingblock. That is, there may be used a method in which, after processedparts each having a desired size and a desired shape are obtained fromthe block-like extrusion molding block, the processed parts are pressedso that cells are flattened so as to be spread in a directionperpendicular to the direction of the thickness, and then the processedparts are annealed if necessary.

[0110] With respect to the processed parts of polystyrene foam havingopen cells, dust, or the like, is hardly produced even if the surface ofpolystyrene foam is rubbed in handling, and polystyrene foam isexcellent both in strength tolerant to atmospheric pressure and inmoderate flexibility necessary for handling, compared with urethane foamhaving open cells as used in the aforementioned first and secondembodiments. Furthermore, not only the shape of a fine cell effectivefor radiation heat insulation is provided but also an effect of blockingoff radiation heat in the heat insulating direction is enhanced byprocessing cells flatly so as to be spread in a direction perpendicularto the direction of the thickness. Accordingly, the processed parts ofpolystyrene foam have various adaptive properties such as excellent heatinsulating property, etc. brought by these effects.

[0111] The thus obtained processed parts of polystyrene foam having opencells are put between the inner box 99 which is formed like a box ofstainless steel thin plates and which constitutes an interior surface,and the outer box 23 which is formed as a 4-side bent article of acolored steel plate and which constitutes an exterior surface. Then, arectangular flat plate-like structural material 26 which has such athickness that the material 26 is slightly protruded outward from theopening surface of the bottom portion of the shell 21 and which hasinclined circumferential surfaces 26 a corresponding to inclinedsurfaces of the outer parts 24 a, 25 a and 35 a of the side wallstructural materials is inserted in the bottom wall portion of the shell21 so that the inclined circumferential surfaces 26 a are made to abuton the inner surfaces of the protrusion portions of the outer parts 24a, 25 a and 35 a, and further, outer circumferential portions 26 b ofthe inner surface of the structural material 26 are made to abut on thebase end surfaces of the inner parts 24 b, 25 b and 35 b of the sidewall structural materials. Further, the end side portions 33 of theplate member 27 covering the bottom wall are inserted in and engagedwith the grooves 32 of a predetermined depth formed by bending the endedge portions of the outer box 23 inward in zigzag as shown in FIG. 2and filled with the adhesive agent 31 of a liquid matter having anadhesive sealing function.

[0112] Then, evacuation is performed through the vacuum valve 28attached to the plate member 27 by means of welding, so that the shell21 constituted by the inner and outer boxes 22 and 23 and the platemember 27 is brought in close contact with the respective structuralmaterials 24,25,26 and 35 inserted therebetween. At the same time, theouter box 23 and the plate member 27 are strongly engaged with eachother at the joint portion 29 by use of mutual attraction force based onnegative pressure produced at the time of evacuation of the inside ofthe shell, and this state is kept until the adhesive agent 31 in thegrooves 32 has hardened, so that jointing and sealing between the outerbox 23 and the plate member 27 are performed. Although the labyrinthinestructure of the side edge portions of the structural materials 24 and25 is not shown here, it is a matter of course that adjacent structuralmaterials are combined with each other in tiers at each of the cornerportions of the side walls.

[0113] Results of evaluation of heat insulating property based on thequantity of leaking heat and design characteristic based on thesmoothness of the wall surface of the shell in comparison between testexamples 1, 2 and 3 and comparative examples 1 and 2 will be describedbelow in order to confirm the heat insulating effect of the full vacuumheat insulation box body according to the aforementioned first, secondand third embodiments.

TEST EXAMPLES 1, 2 AND 3

[0114] For the use of a chest freezer having an internal volume of 280L, the following test examples 1 through 3 were prepared by theproducing method explained in the first embodiment. That is, a fullvacuum heat insulation box body (test example 1) according to the firstembodiment was formed by using structural materials with no gas-exhaustgroove which were formed by cutting a slab of urethane foam having opencells and processing the cut out pieces; another full vacuum heatinsulation box body (test example 2) according to the second embodimentwas formed by using structural materials which were formed by providingeach structural material according to the test example 1 with grooveseach having a width of 3 mm and a depth of 5 mm, arranged at intervalsof a pitch of 50 mm; and a further full vacuum heat insulation box body(test example 3) according to the third embodiment was formed by usingstructural materials formed through steps of pressing a slab ofpolystyrene foam having open cells so as to make the cells flat tospread in a direction perpendicular to the direction of the thickness,annealing the slab if necessary, and cutting pieces out of the slab andprocessing them.

COMPARATIVE EXAMPLE 1

[0115] The shell obtained by the method of fitting the shell materialsand the respective parts explained in the first embodiment was attachedto a jig in a state where the opening portion of the shell which is asurface opposite to the opening portion of the inner box was placedupward so that the shell was not deformed by foaming pressure of foamingurethane. Then, raw materials of two-part foaming urethane containingcyclopentane as a foaming agent were discharged while mixed by use of amixer of a high-pressure foaming machine so that the raw materials wereinjected into the shell in a direction along the bottom surface from aninjection hole located in a machine chamber in the body portion of thechest freezer. Then, the hole used for injection was sealed immediatelyso that foaming urethane did not leak. When a reaction of the two-partraw materials was started, the mixture solution flew in the form ofproduced bubbles while being foamed on the basis of vaporization ofcyclopentane caused by reaction heat of a resinification reaction andgeneration of carbon dioxide gas as a byproduct of the resinificationreaction. As a result, gaps in the shell were filled with the mixturesolution. After the shell was left for 5 minutes during which hardeningof the mixture solution was completed, the shell was taken out from thejig. Thus, there was obtained a heat insulation box body filled withclosed cells in this comparative example 1.

COMPARATIVE EXAMPLE 2

[0116] Two-part foaming urethane having open cells was injected into theshell in the same manner as in the comparative example 1 so that theshell was filled with the foaming urethane. After hardening wascompleted, the shell was taken out from the jig to thereby obtain a heatinsulation box body in this comparative example 2. Incidentally, in thecomparative example 2, a vacuum cock was provided in a machine chamberlocated in its bottom portion and for receiving a compressor, etc.

[0117] The content of evaluation is as follows.

[0118] (1) Heat insulating property

[0119] The quantity of leaking heat and the change thereof with thepassage of time were evaluated.

[0120] The quantity of leaking heat was obtained on the basis ofelectric energy which was given when the inside of a chest freezerequipped with a heater of known heating power in its center portion waskept at an arbitrary temperature in the condition that the chest freezerwas put in an thermostatic chamber kept at another arbitrarytemperature.

[0121] In this occasion, the chest freezer was put in an thermostaticchamber at 20° C. in order to secure 50° C. as the temperaturedifference between the inside of the freezer and the outside of thefreezer in an actual use state, and in this state, electric energy givento the heater was adjusted and stabilized so that the temperature of theinside of the freezer is kept to 30° C. The quantity of given heat wascalculated on the basis of given electric energy per unit time and usedas the quantity of leaking heat.

[0122] Incidentally, a chest freezer produced herein was used when thetime longer than 48 hours was passed after the completion of evacuation.A door having a heat insulation layer filled with closed-cell urethanefoam was used for the opening portion of the chest freezer in common tothe test examples 1 and 2 and the comparative examples 1 and 2.

[0123] (2) Efficiency in Evacuation

[0124] The time required from the start of evacuation by use of a vacuumpump having a gas-exhaust capacity of 1500 L/min to the end when avacuum value of 0.05 torr is confirmed by use of a Pirani vacuum gaugedisposed in a portion of a vacuum cock, was measured. After the heatinsulation box body was held for 60 seconds after the confirmation ofthis value, the vacuum cock was closed so that air, or the like, did notenter the heat insulation box body from the outside. Thus, theevacuation of the heat insulation box body was completed.

[0125] The degree of vacuum after 2 hours and the degree of vacuum after48 hours from the completion of the evacuation of the heat insulationbox body were measured by use of the Pirani vacuum gauge.

[0126] Efficiency in evacuation was evaluated on the basis of the timerequired for evacuation and the quantity of reduction of the degree ofvacuum.

[0127] (3) Design Characteristic in External Appearance

[0128] A result of comparison of smoothness in external appearance byeye observation was evaluated as design characteristic in externalappearance so as to be classified into five-stage levels based on thecomparative example 1 representing a conventional product.

[0129] Results of the items (1) to (3) are shown in the followingTable 1. TABLE 1 Test Test Test Comp. Comp. Ex. 1 Ex. 2 Ex. 3 Ex 1 Ex. 2Quantity of Leaking Heat 30.6 31.0 27.3 47.7 38.5 (kcal/h) VacuumReaching Time 162 152 172 — 282 (sec) Chang of 2 hours 0.06 0.06 0.11 —0.47 Degree of 48 hours 0.08 0.07 0.13 — 1.06 Vacuum with the Passage ofTime (torr) Smoothness of Outer 4 4 4 3 2 Box

[0130] As was apparent from results of Table 1, it could be confirmedthat all the test examples 1, 2 and 3 had remarkably excellent heatinsulating property compared with the comparative example 1 showing aconventional heat insulation box body using closed-cell urethane foammade with cyclopentane as a foaming agent.

[0131] Further, the heat insulating property in all the test examples 1,2 and 3 was enhanced compared with a heat insulation box body filledwith open cell foaming urethane directly injected as shown in thecomparative Example 1.

[0132] As a factor thereof, the evacuation time is shortened and thequantity of gas remaining in the inside of the shell is small after thecompletion of evacuation, because structural materials cut off from aslab of foamed article are used in the present invention. This fact wasconfirmed from the degree of vacuum kept high and the small quantity ofleaking heat providing excellent heat insulating property.

[0133] Particularly with respect to the test example 3, reduction in thequantity of leaking heat was achieved with remarkable enhancement ofheat insulating property. It is believed that the enhanced insulationability is due to the effect obtained by use of open cell polystyrenefoam and by flattening the shape of each cell so as to spread the cellin a direction perpendicular to the direction of the thickness.

[0134] Further, it was found that the smoothness of the outer box in thecomparative example 2using open cell urethane foam as a structuralmaterial was slightly lowered compared with the comparative example 1representing a conventional heat insulation box body filled withclosed-cell urethane foam without use of vacuum heat insulation so thatthe comparative example 2 was inferior to the comparative example 1 inexternal appearance design characteristic.

[0135] On the contrary, the test examples 1, 2 and 3 according to thepresent invention were not inferior in external appearance designcharacteristic to the comparative example 1 representing a conventionalproduct, so that the test examples 1, 2 and 3 could obtain good results.

[0136] External appearance design characteristic greatly depends on theuniformity of the heat insulating material packed in the inside of theshell. Accordingly, in the case of a large-size refrigerator, theflowing distance of foaming urethane becomes very long. Accordingly, inthe case of comparative examples, a large difference in the shape offlowing bubbles is generated between the start point of foaming and thefinally filled portion and, further, flowing bubbles tend to be combinedwith one another to change the flow of the bubbles. As a result,mechanical properties such as compression strength, etc. vary widely inaccordance with the respective portions. That is, non-uniformcontraction is created because of the fact that the inside temperatureraised up to about 120° C. by a exothermic reaction and is cooled to theroom temperature after the completion of foaming, or because of thedifference of the environmental temperature of use, or the like.

[0137] The fluidity of bubbles in foaming of open cell foaming urethaneis further inferior to that in closed-cell foaming urethane.Accordingly, in foaming of open cell foaming urethane, theaforementioned disadvantage occurs easily and closed cells are apt toremain in the vicinity of the wall surface of the shell where shearingstress caused by the flowing of the bubbles is not applied to thebubbles so that the closed cells which are apt to be deformed due to achange of the temperature are distributed ununiformly. It is consideredthat this is a factor which tends to degrade the external appearancedesign characteristic.

[0138] On the contrary, in structural materials used in the full vacuumheat insulation box body, the slab of foamed article is so configuredthat a foaming urethane mixture solution applied uniformly is foamedonly upward. Accordingly, the physical property distribution is quiteuniform, and moreover, it is possible to cut structural materialsselectively from a portion near the center of the slab where most of thepores are communicated with one another, so that deformation hardlyoccurs in the structural materials.

[0139] Further, in open cell urethane foam packed in the heat insulationbox body, foaming gas remains in the inside as it is, and remaining ofunreacted components, adsorption of the foaming gas onto the resin, etc.occur frequently.

[0140] On the contrary, in the case of a slab of urethane foam, foamingis performed in an opened state and structural materials are cutselectively from a portion near the center where most of the pores arecommunicated with one another. Accordingly, it is unnecessary to keep astate where an excessive amount of foaming gas remains in pores so as tobe adsorbed easily. Furthermore, on a single structural material cutout, processes such as heating, drying under a vacuum state, etc. can becarried out easily, so that extremely stable physical properties can beobtained and the quantity of gas produced from the structural materialscan be suppressed in a state where the inside of the heat insulation boxbody is in a vacuum. Accordingly, degradation of heat insulatingproperty depending on the degree of vacuum is further suppressed so thatreliability against vacuum loss from the inside over time can beenhanced and the operating time of an evacuator used for maintainingvacuum can be shortened. As a result, more power saving is attained inthe chest freezer using this heat insulation box body.

[0141] Here, a notable result is obtained in comparison between the testexamples 1 and 2. That is, though both full vacuum heat insulation boxbodies exhibit good heat insulating property and are sufficientlyeffective compared with the comparative examples 1 and 2, it is foundthat, in the case of the test example 2 using the structural materialsprovided with gas-exhaust grooves, the grooves do not affect itsexternal appearance design characteristic and that the time required forevacuation is shortened to thereby enhance easiness of evacuation.

[0142] Embodiment 4

[0143] Referring now to FIGS. 9-12, the inside of the circumferentialside walls will be explained by illustrating only the right walls.

[0144] The full vacuum heat insulation box body in this embodiment isapplied to a refrigerator. The inner box 22 having an uneven shape 22 aon its surface and constituting an interior surface of the shell 21 isformed in such a manner that a complex sheet material constituted bypolystyrene resin containing butadiene rubber as a middle layer,acrylonitrile, which has an excellent gas barrier property as an upperlayer and polypropylene as a lower layer is prepared, silicon is alsodeposited on the surface of the upper layer, and the thus obtained sheetis molded in a vacuum into the inner box 21.

[0145] Further, the outer box 23 constituting an exterior surface of theshell 21 is formed of a bent member which is a colored steel plateshaped in the form of a hollow box integrating a ceiling, a floor andopposite sides. An end side portion 33A of the inner box 22 is insertedinto a groove 32A which is formed by bending an end edge portion of theouter box 23 inward and in a zigzag configuration, as shown in FIG. 10,so that the groove 32A has a predetermined depth and is filled with anadhesive agent 31 of a liquid substance having an adhesive sealingfunction. Thus, the outer box 23 and the inner box 22 are joined to eachother. The configuration of the joint portion including the adhesiveagent 31 is the same as the joint portion between the plate member 27and the outer box 23 as described previously in the first embodimentwith reference to FIG. 2. A wide reservoir portion 34A for reserving theadhesive agent 31 is provided in the upper portion of the groove 32A.

[0146] A structural material 25A to be inserted in the inside of each ofthe opposite side walls, ceiling, floor and a middle wall in the shell21 is constituted by two parts 25 a and 51. Among these parts, the part25 a having a simple shape constituted by planes is inserted in a smoothsurface portion of the shell 21, that is, a portion on the outer box 23side in the ceiling, floor and middle wall and opposite side walls. Thepart 25 a exhibiting a triangular sectional structure is cut out from alarge slab of foamed article obtained by foaming, a foaming resin suchas foaming urethane, or the like, having open cells. Further, the part51 to be inserted in the shell on the side of the inner box 22 having anuneven surface shape 22 a for shelf rests, cooled air circulatinggrooves, etc. also exhibits a triangular sectional structure basically.However, if the part 51 is formed, for example, of a simple plate-likestructural material, the structural material does not fully abut on theuneven-shape portions such as shelf rests, etc., so that theuneven-shape portions may be deformed by the atmospheric pressure whenthe shell is evacuated. Therefore, the structural material part 51 whichcan fully abut on the inner box 22 is formed of a compression moldingcapable of having a free shape by using a mixture consisting of powderobtained by pulverized urethane foam and an adhesive agent melted byheating, so that the part 51 is made to have a desirable shape followingshelves, cooled air circulating grooves, etc. As the powder used herein,a pulverized resin foam such as foam of polystyrene, urethane, phenol,urea, or the like, having open cells is preferably used. However, aninorganic foam such as pearlite or particles of inorganic substance orresin may be used. Incidentally, it is preferable that gas-exhaustgrooves as described in the aforementioned second embodiment withreference to FIG. 8 are provided in the inner surface of the outer boxside part 25 a of the structural material 25A. Other configurationsincluding the configuration (labyrinthine structure) of corner portionsof side wall structural materials and ceiling and floor structuralmaterials, the configuration of the joint portion between the outer box23 and the plate member 27, the composition of the adhesive agent 31,etc. are the same as those in the aforementioned embodiments.

[0147] A method for producing a refrigerator formed from the full vacuumheat insulation box body configured as described above will be describedbelow on the basis of the flow chart of FIG. 12 and with reference toFIGS. 9 through 11.

[0148] First, a sheet is obtained by vapor deposition of silicon on aninner surface of a complex sheet material which consist of polystyreneresin containing butadiene rubber as a base material, acrylonitrileexcellent in gas barrier property arranged on the inner side of the heatinsulation wall, and polypropylene arranged on the outer side of theheat insulation wall. The thus obtained sheet is shaped into a boxhaving upper and lower compartments by vacuum molding to thereby obtainan inner box 22 which has an uneven shape 22 a in its surface andconstitutes an interior surface of the shell of the refrigerator. Then,a hollow bent article integrating a ceiling, a floor and opposite sidesis prepared by bending a colored steel plate to thereby obtain an outerbox 23 which constitutes an exterior surface of the shell of therefrigerator. After the inner box 22 is inserted into the outer box 23,they are joined to each other at joint portions to form a first shellwhich is opened in the back of the outer box (step 211). The work ofjoining the outer box 23 and the inner box 22 is as follows.

[0149] As shown in FIG. 10, the groove 32A provided in the outer box 23is filled with the aforementioned adhesive agent, specifically anadhesive agent 31 obtained by mixing a liquid resin such as an epoxyresin, or the like, with ceramics such as a metal oxide, or the like.After an end side portion 33A of the inner box 22 is inserted into thegroove 32A filled with the adhesive agent 31, this inserted state isheld until the adhesive agent 31 in the groove 32A has been hardened tothereby perform joining and sealing between the outer box 23 and theinner box 22. In this occasion, the adhesive agent 31 is charged more inthe vicinity of the center of each groove to make it flow by theinsertion of the inner box end side portion 33A, so that the groove 32Acan be entirely filled with the adhesive agent 31 and uniform andfaultless sealing is preferably obtained. By immersing the end sideportion 33A of the inner box 22 in the resin in the groove 32A formed inthe outer box 23 in the aforementioned manner, defects such asincompletely joined portions, and communicating portions, etc. can beeliminated, so that a refrigerator shell structure in which the jointportions are perfectly sealed is obtained. As a result, defect portionssuch as holes passing through the shell, etc. are reduced to secure asealing structure having superior reliability in blocking of gas such asair, water vapor, etc. entering the heat insulation box body from theoutside.

[0150] Then, structural materials to make the shell endure theatmospheric pressure to prevent the deformation of the shell during theevacuation work in the posterior step are prepared, inserted into thefirst shell, and then sealed with a plate member 27 from the outside(step 212). The preparation of the structural materials is as follows.First, a mixture consisting of powder of pulverized urethane foam and anadhesive agent melted by heating is compression-molded into a desirableshape following shelves, cooled air circulating grooves, etc. in theinner box 22 to thereby obtain a first structural material, that is, astructural material part 51 basically exhibiting a triangular sectionalstructure. Further, a foaming resin such as foaming urethane, or thelike, having open cells is foamed to prepare a large slab of foamedarticle. Second and third structural materials are cut out from thislarge foamed article. That is, the second structural material is a part25 a having a triangular sectional structure so as to be disposed on theouter box 23 side, face to face with the structural material part 51 anda third structural material is a structural material 26 having a shapelike a flat plate so as to be inserted in the opening portion in theback of the first shell. The structural materials thus obtained areinserted in the first shell through the opening in its back.

[0151] The insertion of the structural materials into the first shellwill now be described in detail.

[0152] First, the first structural materials, that is, the structuralmaterial parts 51 are inserted in the inside of the side walls along theinner box 22 having protrusion portions such as shelves, etc. from theopening in the back of the first shell with the base portions of thestructural material parts 51 as the forefronts. The second structuralmaterials, that is, the smooth-surface parts 25 a are inserted in theflat ceiling and middle wall from the opening of the back of the firstshell with the base portions of the parts 25 a as the forefronts. Then,a second structural material, that is, a part 25 a is inserted on theouter box 23 side in the side walls face to face with the structuralmaterial parts 51 from the opening in the back of the first shell withthe vertex portions of the parts 25 a as the forefronts. Other secondstructural materials, that is, other parts 25 a are inserted also in theceiling and middle wall on the opposite side to the previously insertedparts 25 a, from the opening in the back of the first shell with thevertex portions of the parts 25 a as the forefronts. In this occasion,the length and thickness of the base portion of a part 25 a insertedlater are preferably adjusted so that the base portion of the part 25 aprojects backward by a slight distance, preferably, about 10 mm from anextension line of the back of the inner box 22, in the same manner as inthe case of a chest freezer in the first embodiment. Accordingly, theinside of side walls and ceiling and middle wall of the first shell isfilled.

[0153] After a bottom plate and a structural material are then disposedin the back portion and a floor corresponding to a machine chamberportion for mounting a compressor, etc., the opening in the back of thefirst shell including the machine chamber is blocked by the flat-platelike third structural material 26 and the joint portion between theplate member 27 and the first shell is sealed by an adhesive agent 31 tothereby form a fully closed second shell (step 213). Then, evacuation isperformed through a not-shown vacuum valve attached to the plate member27 (step 214). Incidentally, the vacuum valve is attached to the machinechamber portion so that the fully closed state can be kept after theevacuation.

[0154] The evacuation is started under the condition that the structuralmaterials 25 a, 51 and 26 put between the inner and outer boxes 22 and23 are not fixed by means of an adhesive agent, or the like, before theadhesive agent 31 in the groove 32 of the joint portion 29 between theouter box 23 and the plate member 27 is hardened. The evacuation iscontinued until the adhesive agent 31 is hardened. Accordingly, when theevacuation is started, the plate member 27 is pulled toward the insideof the second shell according to the pressure difference between the airpressure of the inside of the second shell and the air pressure of theoutside thereof. As a result, the plate member 27 functions as a pistonfor pressing the third structural material 26 from the back side. Theparts as the second structural materials 25 a inserted in the sidewalls, ceiling and middle wall of the shell 21, are successively pressedby the third structural material 26 pressed by the plate member 27, sothat the wedge effect is produced. As a result, there is no slack in thedirection of the thickness of each wall, so that the shell can besubstantially entirely filled without any gap. Accordingly, even in thecase where the inside of the shell reaches a vacuum state, the shell isnever deformed by the atmospheric pressure. Thus, an excellent externalappearance state can be kept. After the adhesive agent 31 is hardened,the inner and outer boxes 22 and 23 and the respective structuralmaterials 25 a, 51 and 26 are kept only by close contact based on avacuum to thereby obtain a refrigerator constituted by a full vacuumheat insulation box body which is light in weight and has a uniformstrength characteristic (step 215).

[0155] Incidentally, it is preferable, from the point of view ofworkability, to use a thixotropic adhesive agent for a portion where thegroove of the joint portion of the shell is inclined horizontally.Further, by adjusting the viscosity of the adhesive agent as mentionedabove, the joint portion between the inner and outer boxes 22 and 23 canbe joined simultaneously with evacuation of the shell. That is, theviscosity values of adhesive agents to be charged in the grooves 32 and32A are adjusted in accordance with the inclination of the joint portion29 between the outer box 23 and the plate member 27 and the inclinationof the joint portion between the inner and outer boxes 22 and 23,respectively, and evacuation is started before the adhesive agents inthe grooves 32 and 32A is hardened, and the evacuation is continueduntil the adhesive agents in the grooves 32 and 32A are hardened.Accordingly, when evacuation is started, not only the plate member 27but also the inner and outer boxes 22 and 23 can be operated as pistonsto press the structural materials from the outside, so that the degreeof mutual contact of the structural materials by means of a vacuum canbe enhanced. Further, because it is predicted that air, water, etc.penetrate the adhesive agents to migrate into the shell, adhesive agentscontaining an inorganic substance are preferably used for the purpose ofsuppressing the penetration of air, water, etc., into the inside of theshell.

[0156] After sealing the joint portion between the outer box 23 and theplate member 27, it is effective to simply evacuate the inside of theshell to form a low vacuum state in a range from about 10¹ to 10² torrto thereby stabilize the inside of the shell so that the plate member 27is attracted to abut on the structural materials.

[0157] By keeping the inside of the shell in a vacuum state in theaforementioned manner, the third structural material 26 is pressed fromthe back side by means of the plate member 27 and the structuralmaterial 25 a is successively pressed by the third structural material26 to thereby produce a wedge effect, so that slack or cavitation in thedirection of the thickness of the wall is prevented. Furthermore,because the plate member 27 is fixed under the condition that themovement and contraction of the structural materials including theaforementioned behavior are stabilized, there is also produced such aneffect that the shell can be prevented from being deformed at the timeof or after full-scale evacuation in the posterior step for providingheat insulating property.

[0158] That is, the shell in the fully closed state after evacuation atthe time of attaching the plate member 27 to the outer box 23 is againevacuated with full-scale evacuation through the vacuum valve after theattachment of the plate member 27, so that gasses such as air, etc.remaining in the shell are exhausted from the shell. Although the degreeof vacuum in the shell in this occasion varies depending on the kind ofthe structural material used, sufficient heat insulating property can beprovided when the degree of vacuum is kept higher than 10⁻² torr,preferably higher than 10⁻² torr. Under these conditions, the vacuumvalve provided in the outer box may be replaced by a sealing valve suchas a check valve, or the like.

[0159] Further, to perform evacuation for keeping a sufficient vacuum inthe inside of continuous pores contained in the structural materials inthe shell with a fully closed structure, it is effective that grooves orholes extending in the direction of the major axis from the portion ofthe vacuum valve or its vicinity are formed in advance, in structuralmaterials formed from a solidified molding of a pulverized urethane foamand a molding cut out from a slab of foamed article. Accordingly,because gasses in pores of structural materials are conducted in thegrooves or holes and exhausted therethrough easily, the time requiredfor evacuation can be greatly shortened.

[0160] If the grooves are wide, they are apt to be deformed by theatmospheric pressure Accordingly, it is rather preferable to providelarge number of grooves each having a depth so as not to hinder handlingof structural materials. When, for example, grooves each having a widthof 3 mm and a depth of 5 mm are formed at intervals of a pitch of 50 mm,a sufficient effect is obtained.

[0161] In order to confirm the heat insulating effect of the full vacuumheat insulation box body according to the fourth embodiment, results ofevaluation of heat insulating property based on the quantity of leakingheat and design characteristic based on the smoothness of the shell wallsurface in comparison of test examples 4, 5 and 6 with comparativeexamples 3 and 4 will be described below.

TEST EXAMPLES 4, 5 AND 6

[0162] By using a refrigerator having an internal volume of 120 L, thefollowing test examples 4 through 6 were prepared by the producingmethod explained in the fourth embodiment. That is, a full vacuum heatinsulation box body (test example 4) was formed by using structuralmaterials which had no gas-exhaust groove, and which were formed bycutting a slab of urethane foam having open cells and processing the cutout pieces; another full vacuum heat insulation box body (test example5) was formed by using structural materials which were formed by cuttinga slab of foam and processing them and which were provided with grooveseach having a width of 5 mm and a depth of 5 mm arranged at intervals ofa pitch of 50 mm; and a further full vacuum heat insulation box body(test example 6) was formed by using structural materials which wereformed by cutting a slab of foam and processing them, and which wereprovided with grooves each having a width of 10 mm and a depth of 5 mmarranged at intervals of a pitch of 50 mm.

COMPARATIVE EXAMPLE 3

[0163] As the steps of the fourth embodiment shown in FIG. 12, a shellcomprising an inner box formed of a vacuum molding of ABS resin fittedinto an outer box formed of a formed product of a colored steel platewith plurality of bent portions was attached to a jig to preventdeforming of the shell by the foaming pressure of foaming urethane.Then, two-part foaming urethane raw materials using cyclopentane as afoaming agent are mixed by means of a mixer of a high-pressure foamingmachine and the mixed solution was injected from holes provided in theneighbors of longitudinal center portions on opposite side walls in theplate member in the back surface of the shell and then the holes usedfor injection were immediately sealed so that foaming urethane did notleak. When a reaction of the two-part raw materials was started, themixture solution flew in the form of produced bubbles while being foamedon the basis of vaporization of cyclopentane caused by reaction heat ofa resinification reaction and generation of carbon dioxide gas as aby-product of the resinification reaction. As a result, gaps in theshell were filled with the mixture solution. After the shell was leftfor 5 minutes during which hardening of the mixed solution wascompleted, the shell was taken out from the jig. Thus, there wasobtained a heat insulation box body filled with closed cells.

COMPARATIVE EXAMPLE 4

[0164] Two-part foaming urethane having open cells was injected into theshell in the same manner as in the comparative example 3 so that theshell was filled with the foaming urethane. After hardening wascompleted, the shell was taken out from the jig to thereby obtain a heatinsulation box body in this comparative example 4. Incidentally, in thecomparative example 4, a vacuum cock was provided in a machine chamberlocated in its bottom portion for receiving a compressor, etc Thecontent of evaluation is as follows. Incidentally, a door used in thesame refrigerator as an existing product was used for the openingportion of the refrigerator in common to the test examples 4, 5 and 6and the comparative examples 3 and 4.

[0165] (1) Weight of Structural Material

[0166] The weight of structural materials put in the shell was measured.

[0167] In all the heat insulation box body, weight increase, that is,the difference between weight before putting in structural materials andweight after putting in structural materials, was employed.

[0168] (2) Heat Insulating Property

[0169] The quantity of leaking heat and the change thereof with thepassage of time were evaluated.

[0170] The quantity of leaking heat was obtained on the basis ofelectric energy which was given when the inside of a refrigeratorequipped with a heater of known heating power in its center portion waskept at an arbitrary temperature in the condition that the refrigeratorwas put in an thermostatic chamber kept at another arbitrarytemperature. As the temperature conditions used in this occasion, thetemperature of the inside of the thermostatic chamber and thetemperature of the inside of each refrigerator as a sample were set to−0° C. and +30° C., respectively.

[0171] (3) Efficiency in Evacuation

[0172] The time required from the start of evacuation by use of a vacuumpump having a gas-exhaust capacity of 1500 L/min to the end when avacuum value of 0.05 torr is confirmed by use of a Pirani vacuum gaugedisposed in a portion of a vacuum cock. After the heat insulation boxbody was held for 60 seconds after the confirmation of this value, thevacuum cock was closed so that air, or the like, did not enter the heatinsulation box body from the outside. Thus, the evacuation of the heatinsulation box body was completed.

[0173] The degree of vacuum after 2 hours and the degree of vacuum after48 hours from the completion of the evacuation of the heat insulationbox body were measured by use of the Pirani vacuum gauge.

[0174] Efficiency in evacuation was evaluated on the basis of the timerequired for evacuation and the quantity of reduction of the degree ofvacuum.

[0175] (4) Design Characteristic in External Appearance

[0176] A result of comparison of smoothness in external appearance byeye observation was evaluated as design characteristic in externalappearance so as to be classified into five-stage levels based on thecomparative example 3 representing a conventional product.

[0177] Results of the items (1) to (4) are shown in the following Table2. TABLE 2 Test Test Test Comp. Comp. Ex. 4 Ex. 5 Ex. 6 Ex. 3 Ex. 4Weight of Structural 3.7 3.7 3.7 2.9 4.4 Materials (kg) Quantity ofLeaking Heat 22.1 22.5 22.7 28.9 26.1 (kcal/h) Vacuum Reaching Time 116108 104 — 155 (sec) Chang of 2 hours 0.06 0.06 0.06 — 0.72 Degree of 48hours 0.08 0.07 0.07 — 1.43 Vacuum with the Passage of Time (torr)Smoothness of Outer 4 4 3 3 2 Box

[0178] As was apparent from results of Table 2, it could be confirmedthat all the heat insulation box bodies of the test examples 4, 5 and 6had remarkably excellent heat insulating property compared withconventional heat insulation box bodies of the comparative examples 3and 4 using closed-cell foaming urethane containing cyclopentane as afoaming agent.

[0179] First, the weight of the structural materials in each of the testexamples 4, 5 and 6 and the comparative example 4 is heavier than thatin the comparative example 3 as a prior art example. This is because thedensity of the structured materials is inevitably increased to obtain astrength necessary for preventing deformation of structural materialscaused by the atmospheric pressure since the inside of the shell is in avacuum state. Particularly with respect to the comparative example 4,the reason (why the weight of the structural materials is heavy) isbecause foaming urethane having open cells is inferior in fluidity, sothat it is necessary to obtain both uniform quality and improved overallmechanical strength by excessive filling of the foaming urethane so asto obtain necessary performance in respective parts of the heatinsulation box body.

[0180] Further, in any of the test examples 4 through 6, evacuatingefficiency is improved and excellent values are exhibited in both heatinsulating property and the loss of vacuum over time, compared with thecomparative example 4 in which foaming urethane having open cells isinjected directly to fill the shell.

[0181] Further, design characteristic in external appearance is alsoimproved compared with the comparative examples 3 and 4. This is basedon the advantage that a low-density large-strength product is obtainedstably in the case of a slab of foamed article whereas in the case ofinjection foaming of foaming urethane having open cells, density andstrength distributions are apt to become wide because remaining ofclosed cells and non-reacted components, absorption of the foaming agentonto the resin, etc. occur frequently and also because the fluidity ofbubbles at the time of formation of the heat insulation box body isinferior so that a uniform product is not obtained, as described in theaforementioned first embodiment.

[0182] In addition, from a slab of foamed-article, it is possible toselectively obtain a portion containing a very large number of opencells, and further, the amount of gasses generated by structuralmaterials under the condition that the inside of the heat insulation boxbody is in a vacuum state can be better suppressed because processessuch as heating of the cut-out structural materials, drying of thestructural materials under a vacuum state, etc. can be made easily.Accordingly, lowering of heat insulating property depending on thedegree of vacuum can be suppressed so that the improvement ofreliability against vacuum loss from the inside over time can beachieved, and further, the operating time of the evacuator can beshortened correspondingly so that more power saving can be achieved withthe refrigerator using this heat insulation box body.

[0183] Further, with respect to the design characteristic in externalappearance, in comparison between the test examples 4 through 6, theuneven portions such as shelf rests, etc. of the inner box are neverdeformed and never dented by the atmospheric pressure exerted by avacuum state kept in the inside of the shell. Further, any of the fullvacuum heat insulation box body exhibits good heat insulating propertycompared with the comparative example 4.

[0184] On the other hand, in the case where gas-exhaust grooves areprovided on surfaces of structural materials located in the centerportion in the direction of the thickness of the wall, slight undulationappears in the test example 6 in which the grooves are wide but designcharacteristic in external appearance is only minimally degraded.

[0185] Further, in the test example 4 in which no groove is provided,there is obtained a result that heat insulating property just afterevacuation is slightly inferior to that in the test example 5.

[0186] Although these results vary in accordance with the hardness andthe size of pores of the structural materials, it is considered that theresults do not so widely depart from the values of this evaluation, whentaking a range satisfying preferable conditions in both the economy andproperties such as heat insulating property, or the like, intoconsideration.

[0187] It is inferred from the above results that the structuralmaterials are most preferably provided with gas-exhaust grooves eachhaving a width of about 5 mm in the neighbor of the center in thedirection of the thickness of the wall.

[0188] In the fourth embodiment, instead of the method of injectingfoaming urethane having open cells into the shell to fill the latterwith the foaming urethane, compression moldings of a mixture ofpulverized urethane foam having open cells and an adhesive agent meltedby heating or moldings cut out from a slab of urethane foam having opencells are used as structural materials. Accordingly, the remainingquantity of dispersion components in a vacuum, such as non-reactedcomponents of foaming urethane, gasses adsorbed onto the foamed resinagent, etc., is reduced and an advantage that a low-densitylarge-strength product is obtained stably can be brought about.

[0189] In addition, in the case of a slab of foamed article, open cellportions located in the vicinity of the center can be selectively cutout and the quantity of gasses generated from structural materials underthe condition that the inside of the heat insulation box body is in avacuum state can be better suppressed because processes such as heatingof the cut-out structural materials, drying of the structural materialsunder a vacuum state, etc. can be made. Accordingly, the lowering ofheat insulating property depending on the loss of vacuum over time canbe suppressed, so that electric energy required for operating arefrigerant circuit and devices pertinent to the refrigerant circuit canbe reduced and also, when, for example, an evacuator is attached to therefrigerator in order to keep the degree of vacuum, the operating timeof the evacuator can be shortened greatly so that more power savings canbe achieved.

[0190] Embodiment 5

[0191] Referring now to FIGS. 13-15, the same parts as those in thefirst, second, third and fourth embodiments are referencedcorrespondingly. Incidentally, only a joint portion between the outerbox and the plate member is representatively shown here as a jointportion of the shell constituent members. As to the joint portionbetween the outer box and inner box FIG. 10 is referred to.

[0192] The full vacuum heat insulation box body in this embodiment isapplied to a chest freezer. The configuration of joint portions betweenconstituent members of the shell 21 constituted by the outer and innerboxes 23 and 22 and the plate member 27 and the configuration ofstructural materials (not shown) inserted in the shell are substantiallythe same as in the aforementioned embodiments. This embodiment isdifferent from the aforementioned embodiments in that a mark 61 as shownin FIG. 14 is provided to indicate a preferable cutting position of theshell surface at the time of disassembling. Here, the mark 61 is formedby a concave line 61 a as shown in FIG. 15.

[0193] In more detail, as shown in FIGS. 13 and 15, the joint portion 29between the outer box 23 and the plate member 27 is constituted by agroove 32 having a predetermined depth which is formed by bending an endedge portion of the outer box 23 inward in zigzag and filled with anadhesive agent 31 of a liquid substance having an adhesive sealingfunction, and an end side portion 33 formed in the plate member 27 whichcan be inserted into a deep portion of the groove 32. The mark 61, thatis, the concave line 61 a is formed in a position which is on the outercircumferential surface of the outer box 23 having the zigzag bentportion and which corresponds to the zigzag bent portion, that is, in aportion 23 c which is opposed to the base end side piece 23 b of thezigzag bent portion.

[0194] Further, if the joint portion between the outer and inner boxes22 and 23 is intended to be used for the cutting position of the shellsurface at the time of disassembling, a mark formed by a concave line,or the like, is given clearly to a position which is on the outercircumferential surface of the outer box 23 having the zigzag bentportion forming the groove 32A shown in FIG. 10 and which corresponds tothe zigzag bent portion.

[0195] That is, a gap which is continuous over the whole circumferenceof the joint portion between the outer and inner boxes 23 and 22 is alsoformed as a groove between the base end side piece 23 b of the zigzagbent portion and a portion 23 a on the extreme end surface of the outerbox 23 opposite to the base end side piece 23 b of the zigzag bentportion. Further, a gap G which is continuous over the wholecircumference of the joint portion 29 is formed between the base endside piece 23 b and the portion 23 c on the outer circumferentialsurface of the outer box 23 opposite to the base end side piece 23 b ofthe zigzag bent portion. Gap G is outside the grooves 32 and 32A, thatis, inside the shell 21, and is a portion which is not filled with theadhesive agent 31, so that this gap is not fixed. Accordingly, bycutting the portion corresponding to the zigzag bent portion on theouter circumferential surface of the outer box 23 (portion of concaveline 61 a) at the time of disassembling, air can be introduced into theshell 21 easily. Because structural materials disposed in the shell 21constituted by the outer and inner boxes 23 and 22 and the plate member27 are fixed to the shell 21 only by close contact by means of a vacuum,the close-contact state of the respective members is released so thatthe members are peeled off and separated easily when the inside of theshell 21 is returned to an atmospheric pressure state by introduction ofair.

[0196] A method for disassembling the full vacuum heat insulation boxbody, that is, the chest freezer configured as described above will bedescribed below with reference to FIGS. 13 through 15 showing the jointportion 29 between the outer box 23 and the plate member 27 cut by wayof example. First, a notch 61 b having a depth of the order of mm,preferably, in a range from 1 to 5 mm, is formed perpendicularly to theouter surface of the outer box along a portion forming a preferablecutting position of shell surface in the joint portion 29 between theouter box 23 and the plate member 27 located on the bottom surface, forexample, along the mark 61 formed by the concave line 61 a provided in aposition corresponding to the reservoir portion 34 in the outer surfaceof the outer box. The notch 61 b is formed over the whole outercircumference of the joint portion 29. The reservoir portion 34 isformed in a predetermined position by use of a roll making machine, orthe like. Accordingly, the aforementioned cutting operation can becarried out efficiently if a cutter 64 provided with a cutting guide 63for guiding the tip of a cutting edge 62 to a position at apredetermined distance from an end side of the outer box 23 as shown inFIG. 13 is used.

[0197] The reason why the shell surface cutting position is set to aposition corresponding to the reservoir portion 34 is that the shellsurface can be cut easily in this position without the necessity ofkeeping high accuracy in the direction of the cutting depth comparedwith the other flat surface portions of the outer box because four steelplates and two or more gap portions are formed in this position by thezigzag bent portion of the outer box 23 and the end side portion 33 ofthe plate member 27 inserted in the groove 32 before the structuralmaterial is reached.

[0198] As described above, the gap G which is continuous over the wholecircumference is formed in the joint portion 29 between the outer box 23and the plate member 27 and also the structural materials disposed inthe shell 21 constituted by the outer and inner boxes 23 and 22 and theplate member 27 are fixed to the shell 21 only by close-contact by meansof a vacuum without use of any adhesive agent. Accordingly, if air isintroduced into the shell 21 through the notch 61 b so that the vacuumstate is eliminated, the close-contact of the structural materials withthe inner and outer boxes 22 and 23 is released so that they arenaturally peeled off and separated easily.

[0199] When the outer circumference of the outer box 23 is cut along themark 61 represented by the broken line in FIG. 14 in the aforementionedmanner and then the plate member 27 capable of being cut off by cuttingthe outer circumference of the outer box 23 is removed, the structuralmaterials can be taken out and recovered easily without injury.

[0200] Further, if the mark 61 is formed by the concave line 61 a asshown in FIG. 15, the cutting edge 62 can be guided by the walls onopposite sides of the concave line 61 a. Accordingly, the cutter 64holding a depth can be used, so that the aforementioned cuttingoperation can be carried out more simply and more easily.

[0201] As described above, in the method for disassembling the fullvacuum heat insulation box body according to the present invention,structural materials can be recovered without injury, so that thestructural materials can be used again as structural materials of asimilar full vacuum heat insulation box body. Further, the shell memberscomprising the inner and outer boxes 22 and 23 joined to each other canbe joined again to the plate member 27 and recycled if a simple repairoperation is carried out, that is, if, for example a new joint portionprepared separately is joined to the shell members or a new jointportion is formed in the plate member 27.

[0202] Further, if all the joint portion between the inner and outerboxes 22 and 23 and the joint portion between the outer box 23 and theplate member 27 are removed, members usable for some other purpose canbe obtained. By melting, or the like, usable raw materials with a smallimpurity content can be also recovered from the members. Accordingly, itis possible to collect members which are usable for various purposes.

[0203] Having now fully described the present invention, it will beapparent to one of ordinary skill in the art that many changes andmodifications can be made thereto without departing from the spirit andscope of the invention as set forth herein. This application is based onJapanese Patent Application No. 10-013873 filed on Jan. 27, 1998 andJapanese Patent Application No. 10-207647 filed on Jul. 23, 1998, theentire contents of which are hereby incorporated by reference.

What is claimed and new and desired to be secured by Letters Patent ofthe United States is:
 1. A vacuum heat insulation box body comprising: ashell comprising inner and outer boxes, and heat insulation walls, theinside of which are to be kept in a vacuum state; and structuralmaterials having continuous pores provided inside said insulation wallsof said shell, and between said inner and outer boxes; wherein saidstructural materials are held to said shell only by close-contact causedby means of a vacuum.
 2. A vacuum heat insulation box body according toclaim 1 , wherein said shell of said heat insulation box body has anuneven surface, and said structural materials abutting said unevensurface include moldings formed of crushed matters of a resin foam.
 3. Avacuum heat insulation box body according to claim 1 , wherein saidstructural materials comprise parts provided with grooves or holes forexhausting air from said continuous pores.
 4. A vacuum heat insulationbox body according to claim 1 , wherein said structural materials areconstituted by a resin foam having open cells.
 5. A vacuum heatinsulation box body according to claim 1 , wherein said structuralmaterials comprise a plurality of triangular-section parts, each of saidtriangular-section parts being disposed in a middle layer of said shellin the direction of wall thickness, or in a layer abutting on an evensurface of said shell.
 6. A vacuum heat insulation box body according toclaim 5 , wherein said triangular-section parts are formed of foamedpolystyrene having open cells.
 7. A vacuum heat insulation box bodyaccording to claim 6 , wherein said foamed polystyrene having open cellsincludes flattened cells which are spread in a direction perpendicularto the direction of wall thickness.
 8. A vacuum heat insulation box bodyaccording to claim 1 , wherein ajoint portion between said inner andouter boxes comprises: a groove of a predetermined depth formed bybending inwardly one of said inner and outer boxes, said groove beingfilled with a liquid substance having an adhesive sealing function; and;an end side portion formed in the other of said inner and outer boxes soas to be insertable into a deep portion of said groove; wherein joiningand sealing of said joint portion are performed by said liquid substanceby utilizing mutual attraction force produced by evacuation of saidshell.
 9. A vacuum heat insulation box body according to claim 1 ,further comprising: an opening portion formed in said outer box, saidopening portion configured to be closed by a plate member, said openingportion configured to allow said structural materials to be insertedinto said shell through said opening portion; a joint portion betweensaid outer box and said plate member comprising a groove of apredetermined depth formed by bending inwardly one of said outer box andsaid plate member, said groove being filled with a liquid substancehaving an adhesive sealing function; and an end side portion formed inthe other of said outer box and said plate member and configured to beinserted into a deep portion of said groove; wherein joining and sealingof said joint portion are performed by said liquid substance byutilizing mutual attraction force produced at the time of evacuation ofsaid shell.
 10. A vacuum heat insulation box body according to claim 8 ,wherein said groove is formed by bending an end edge portion inwardly ina zigzag configuration.
 11. A vacuum heat insulation box body accordingto claim 8 , wherein said groove has a wide reservoir portion in itsupper portion for reserving the liquid substance so as to prevent itfrom overflowing from the groove.
 12. A vacuum heat insulation box bodyaccording to claim 8 , wherein said liquid substance is constituted byan adhesive agent containing particles or powder of a metal oxide or ametal nitride.
 13. A vacuum heat insulation box body according to claim10 , wherein an indicia is provided in the outer circumferential surfaceof the zigzag bent portion.
 14. A method for producing a vacuum heatinsulation box body, comprising the steps of: integrating an inner boxand an outer box into a shell which is opened in an open bottom surfaceof said outer box; inserting a first structural material havingcontinuous pores and a triangular section into a space formed betweenthe inner and outer boxes first shell through the opening of said firstshell, by inserting a bottom side portion of said first structuralmaterial first; inserting a second structural material having continuouspores and a triangular section into said space through said opening ofsaid first shell by inserting a vertex portion of said second structuralmaterial first to thereby fill said space of said first shell; blockingthe opening of said first shell with a third structural material havingcontinuous pores and a shape of a flat plate; enclosing said thirdstructural material with a plate member to seal the joint portionbetween said plate member and said first shell to thereby fully closesaid shell; and evacuating said second shell.
 15. A method for producinga vacuum heat insulation box body according to claim 14 , wherein saidfirst structural material is to be brought into contact with an unevensurface of the shell is first inserted, then said secondtriangular-section structural material having no uneven surface isinserted with a vertex portion thereof inserted first, so that saidspace of said first shell is filled with said structural materials. 16.A method for producing a vacuum heat insulation box body according toclaim 14 , wherein evacuation of said second shell is performed underthe condition that said inner and outer boxes and said structuralmaterials inserted between said inner and outer boxes are not fixed byan adhesive agent, or the like.
 17. A method for producing a vacuum heatinsulation box body according to claim 14 , further comprising the stepsof: bending at least one member of said first shell and said platemember for covering said opening of said first shell at the jointportion to form a groove of a predetermined depth; filling said groovewith a liquid substance formed of an adhesive agent containing particlesor powder of a metal oxide or a metal nitride; and solidifying saidliquid substance after the other member of said first shell and saidplate member is inserted into said groove which is filled with saidliquid substance, while evacuating said fully closed second shell tothereby perform both joining and sealing at said joint portion.
 18. Amethod for disassembling a vacuum heat insulation box body having ashell constituted by inner and outer boxes, and structural materialsdisposed in said shell, said inner and outer boxes and said structuralmaterials being fixed by close-contact caused by means of a vacuum,comprising the steps of: cutting a surface of said shell to therebyintroduce air into the inside of said shell so as to allow the insidestate of said shell to return to an atmospheric pressure state; andseparating inner and outer boxes of said shell and said structuralmaterials from each other.
 19. A method for disassembling a vacuum heatinsulation box body according to claim 18 , wherein in said full vacuumheat insulating box body, a joint portion between said inner and outerboxes is constituted by a groove formed by bending an end edge portionof one of said inner and outer boxes inward in a zigzag configuration,wherein said groove is filled with a liquid substance, and wherein anend side portion is formed in the other of said inner and outer of saidboxes so as to be able to be inserted into a deep portion of saidgroove; wherein said cutting step further comprises providing a notch inan outer surface of said one member having the zigzag bent portion alonga position corresponding to said zigzag bent portion; and separatingfrom each other said inner and outer boxes of said shell and saidstructural materials.
 20. A method for disassembling a vacuum heatinsulation box body according to claim 18 , wherein in said vacuum heatinsulating box body, said outer box has an opening portion used forinserting structural materials which is blocked with a plate member, anda joint portion between said outer box and said plate member isconstituted by a groove formed by bending an end edge portion of onemember of said outer box and said plate member inward in a zigzag andfilled with a liquid substance, and an end side portion is formed in theother of them so as to be inserted into a deep portion of said groove;wherein said cutting step further comprises providing a notch in anouter circumferential surface of said one member having the zigzag bentportion along a position corresponding to said zigzag bent portion; andsaid outer box and said plate member are then separated from each otherand the materials of said shell and said structural materials arerecovered.